The present invention relates to the oxidation of halogenated organic compounds. In particular, the invention relates to a method for oxidizing halogenated organic compounds in the presence of a carbonaceous catalyst.
Halogenated organic compounds are useful for a number of purposes. In most applications of these materials, particularly in their use as solvents, the spent materials are discarded. Furthermore, the production and use of these halogenated organic compounds often result in the production of unwanted halogenated organic compound by-products. Unwanted by-products also are produced in processes employing halogenated organic compounds as intermediates. These unwanted by-products represent a waste of both the halogen and organic compounds thereof. It has been suggested that spent and unwanted halogenated organic compounds be further processed to provide useful materials, but often the capital investment required for such an operation far exceeds the economic justification for the further processing. Therefore, these unwanted halogenated organic compound by-products must be discarded.
Disposal of halogenated organic compounds is complicated by the fact that these compounds cannot merely be released to the atmosphere or flushed away with water without causing serious pollution problems. The pollution problems arise because of the carcinogenic properties, the toxicity of some of the halogenated organic compounds, their immiscibility with water, and in many cases, their chemical stability which prevents them from breaking down readily into harmless waste products.
Typical disposal methods for the undesirable halogenated organic compound by-products consist primarily of terrestrial burial methods. These disposal methods include ocean discharge, open pit burning, drum burial, and deep-well disposal. However, these methods have engendered serious criticism as being hazardous to the environment and are known to have contaminated ground water. In addition, these methods are economically unattractive because the cost of the disposal of the unwanted halogenated organic compound by-product is not diminished by recovery of some material of significant economic worth.
Incineration of the undesirable halogenated organic compound also has been proposed. U.S. Pat. No. 3,453,073 discloses a process for recovering halogen from halogenated hydrocarbons comprising passing a chlorinated hydrocarbon, water and oxygen over catalysts at elevated temperatures to form oxides of carbon, water, and hydrogen chloride. This process, however, requires the utilization of elevated temperatures which requires special equipment that is stable at such high temperatures and will resist corrosion by the hydrogen chloride and water produced. The production of carcinogenic materials such as dioxin also is a serious impediment to this mode of disposal.
U.S. Pat. Nos. 1,989,806 and 3,989,807 propose a process for the recovery of chlorine from chlorinated organic compounds which comprises catalytically oxidizing a chlorinated organic compound feed by reacting the chlorinated organic feed with oxygen or an oxygen-containing gas at a reaction temperature of below 500.degree. C. and in the presence of a transition metal-containing supported catalyst. The catalytic supports employed in this method include zeolite materials and activated alumina. U.S. Pat. Nos. 4,059,677 and 4,065,543 also disclose a method for recovering halogen from halogenated organic compounds which comprises reacting the halogenated hydrocarbon with oxygen at relatively mild temperatures in the presence of a metal oxide catalyst system. The metal oxide catalyst system utilized in this method includes manganese oxide and cobalt oxide. U.S. Pat. No. 4,423,024 also proposes a method for oxidizing a halogenated organic compound comprising re-heating a mixture of the halogenated hydrocarbon, oxygen, and, where necessary, water and contacting this mixture with a molecular sieve catalyst at relatively mild temperatures.
There also are known methods for regenerating saturated catalysts used to remove harmful organic compounds from water, soil or air. Typical regeneration methods include steam regeneration, superloading the catalyst and solvent regeneration. These methods have the drawback that although the catalyst may be regenerated, the steam or solvent effluent stream remains contaminated by the harmful organic compound and must be treated before disposal.